1. Field of the Invention
This invention relates to a damping valve for hydraulic pressure pulses produced by a positive displacement pump in dispensing fluid, especially in dispensing liquid chemicals for semiconductor industry.
2. Background Information
In many practical fields, fluid is transported and delivered from one location to another with a positive displacement pump. Pressure pulses within the fluid produced by the pumps induce various problems for the fluid and transport system. For example, when semiconductor manufacturers dispense ultra-pure corrosive chemicals with a dual diaphragm pump from chemical containers to user stations, pressure pulses produced by the diaphragm pump will induce particulate impurity shedding from the components of the dispensing system. When fuel is supplied to combustion chambers (e.g., in vehicles) with an electric reciprocating fuel pump, the fluid flow (and therefore the combustion) is not stable because of the pressure pulsation created by the pump. Such non-stable flow or the pressure pulses also produce undesirable noise.
A common practice for eliminating pulsation problems is to install a pressure pulse damper right after the pump. Numerous pulsation-damping devices are found in the prior art, and the effectiveness of a pulsation damper is limited either by its construction or by its functioning principles. With the dampers described in U.S. Pat. Nos. 5,797,430, 5,868,168, and 5,904,181, all of which are hereby incorporated by reference in their entirety, a flexible wall is used to absorb fluid pulses by deforming it upon subjection to fluid pulsation. This flexible wall can be a diaphragm, a membrane, or a bellows, which moves back and forth between a chamber with compressible air or gas and a chamber with fluid to absorb the pressure pulses. Since a pressure pulse propagates along the flowing direction of fluid while it is deforming the flexible wall, it will not be effectively absorbed and damped, and therefore the problems related to pressure pulsation in fluid remain. Also, this type of damping device is operable only within a limited operation pressure range in which they are originally designed or adjusted. The pressure of fluid and a pulse beyond the limit will result in excessive deformation of the flexible wall and therefore failure of the damping function.
For preventing a flexible wall from excessive deformation or failure, a compressible gas chamber with adjustable gas pressure has been proposed in U.S. Pat. No. 4,556,087, hereby incorporated by reference in its entirety. Upon pressure change of fluid in which pressure pulses exist, high-pressure gas or air is allowed to flow in or out of the compressible gas chamber to adjust the pressure against the fluid pressure at the other side of the flexible wall. However, pressure pulses may not be effectively damped because of the propagation of pressure along the flowing direction of fluid. Another drawback is that the construction of this damping device is complicated. Another damping device is based on a counter flow concept, as described in U.S. Pat. No. 5,133,647, hereby incorporated by reference in its entirety. The fluid with pressure pulses is divided into two flows at opposite directions, based on a concept that the pulses cancel out when these two flows merge together. Since the fluid may not be compressible and the propagation of pressure pulses is along the fluid flowing direction, a pulse could be segregated into two or more pulses and, in many cases, the damping device may not function at all when the two separated flows are mismatched.
As it has been realized, those pressure dampers that can be found in the prior art do not meet users"" needs for a highly effective and reliable pressure pulse damper.
Accordingly, the present invention is directed to providing a pressure pulsation-damping valve that effectively damps pressure pulses in fluids by avoiding the disadvantages of the devices as described in the prior art.
According to an exemplary embodiment of the present invention, a system for damping pressure pulses is provided, including a channel for permitting fluid flow between a first chamber and a second chamber, a piston for varying a fluid flowing space such that pressure pulses in fluid are damped, and a flexible wall for absorbing pressure pulses in fluid, wherein the flexible wall is connected to the piston by a transmitting rod such that a movement of the piston results in a deformation of the flexible wall and vice versa.
According to another embodiment of the present invention, a method for damping pressure pulses in a fluid is provided, including the steps of permitting fluid flow between a first chamber and a second chamber, varying the fluid flow such that pressure pulses in the fluid are damped, and absorbing pressure pulses in the fluid, wherein the steps of varying and absorbing are performed substantially at the same time.
To achieve the objects of the present invention, a fluid pressure pulsation-damping valve that can be installed in a fluid dispensing line is provided with the features of damping pulses in fluid by both a movable wall and a movable piston type of part. The whole damping valve consists of housing with a cylinder shape, a movable wall, a transmitting rod, a damping piston, and necessary connection parts. The housing is partitioned into three chambers by a movable wall and a solid separation wall with a nozzle. Two of the chambers provide the channels for fluid flowing through, and the other one is either filled with compressible air or gas, or installed with a supporting spring inside to allow the movable wall to move back and forth into this chamber.
The movable wall and the damping piston are conjugated with the transmitting rod and mounted inside the housing. The transmitting rod is arranged to pass through the nozzle to form an annular channel for fluid, and fixed on the movable wall at one end and on the damping piston at another end. The movable wall is fixed on the housing as a partition wall for the compressible air chamber and one of the fluid chambers. The movable damping piston is located in the fluid chamber that is formed by the non-movable wall of the housing with a nozzle and another end of the housing. Two openings on the housing wall at separated locations allow the communication of fluid between outside fluid conduits and the damping valve. The damping valve starts to function upon a pressure pulse either applied to the movable piston or the movable wall, and the transmitting rod ensures concurrent movement of the two movable parts. The movable wall absorbs the pressure pulse by its outward movement to the compressible air chamber, and the movable piston damps the pressure pulses by restricting the fluid flow when it passes through an annular channel of changed size. Therefore, the two movable parts effectively damp pressure pulses.
Besides being highly effective, the present invention also has the advantages of being easy to use, easy to manufacture, easy to maintain, and cost effective because of its simple construction. The operation of the present pressure-damping valve is also highly reliable because of its very limited number of parts and straightforward layout.